JP2002122981A - Reflective photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflective photomask capable of preventing the damage of the surface of a reflecting layer in a production process without complexing the production process. SOLUTION: The reflective photomask 10 has a substrate 11 comprising Si, glass or the like, a reflecting layer 12 formed on the substrate 11 and comprising a multilayer film obtained by alternately laminating Mo and Si, a buffer layer 13 formed on the reflecting layer 12 and comprising Ru and an absorbent pattern 14 formed on the buffer layer 13 with a prescribed pattern shape and comprising a material capable of absorbing soft X-rays, e.g. TaN.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reflective photomask, and more particularly to a reflective photomask suitable for use in a high resolution photolithography technique using soft X-rays in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art In a photolithography process of a semiconductor manufacturing process, as design rules are reduced for higher integration, an exposure technology having a higher resolution than the current technology is required. Currently, DUV
Exposure technology using (deep-ultraviolet) light has a wavelength of 2
Exposure with a drawing size of about 250 nm is possible by using a 48 nm light source. On the other hand, a new DUV exposure technique using a shorter light source having a wavelength of 193 nm is expected to be able to expose a drawing size of about 100 to 130 nm. Further, when an exposure wavelength in an EUV (extream-ultraviolet) region called a soft X-ray is used as an exposure technique for realizing a drawing size of 100 nm or less, it is expected that a drawing size of about 5 to 70 nm can be exposed. Currently, research on this is being actively conducted.

An exposure technique using EUV is a conventional DU.
There is a remarkable difference from the exposure technique up to the V region. That is, in the EUV region, most of the materials have a large light absorbing property, so that a reflective photomask must be used unlike the existing transmissive photomask. A general EUV photomask is formed by forming a pattern made of an absorber capable of absorbing EUV light on a mirror (reflecting mirror) having a high reflectance in the EUV region.
Therefore, a region where the surface of the reflector is covered with the absorber pattern is an absorption region, and a region where there is no absorber pattern and the surface of the reflector is exposed is a reflection region. The reflecting mirror used here is formed by alternately laminating different kinds of films such as molybdenum and silicon (Mo / Si) and beryllium and silicon (Be / Si) to form a multilayer film.

FIG. 11 shows the structure of a photomask 110 of this type. A reflective layer 112 composed of the above-mentioned multilayer film is formed on a substrate 111 of silicon, glass or the like, and a desired pattern is formed on the reflective layer 112. Tantalum nitride (Ta
N) A soft X-ray absorber pattern 113 made of a film or the like is formed.

However, as shown in FIG. 11, in the structure in which the absorber pattern 113 is formed directly on the reflective layer 112, the exposed portion of the reflective layer surface is etched and damaged when the absorber is patterned (etched). As a result, there arises a problem that the reflectance is reduced. After the absorber pattern is further formed, as shown in FIG. 16, defects in the absorber pattern 113 (for example, a portion 113a of an etching residue in the absorber pattern at the left end in FIG. 16, and a chipped portion 113b in the adjacent absorber pattern). When a focused ion beam (hereinafter, referred to as F)
IB) may be used to correct these defects. That is, only the residue portion 113a is locally removed by the etching action when the FIB is irradiated, or the absorber is locally deposited on the chipped portion 113b by irradiating the FIB in a predetermined gas atmosphere. Can be embedded. This step is referred to as a mask repair step. In the structure shown in FIG. 11, there was a sufficient risk that the FIB irradiation might damage the reflective layer surface even in this mask repair step.

Therefore, as a method for solving this problem,
The following two methods have been proposed. The first method uses a photomask having the structure shown in FIG.
o et al., "Process Scheme for Removing Buffer Layer
on Multilayer of EUVLMask ", Digest of papers, Phot
omask Japan p.75,2000. In the photomask 120, a buffer layer 123 made of a silicon oxide film (SiO _x ) is formed below the absorber pattern 124. When manufacturing the photomask 120,
As shown in FIG. 13A, a reflective layer 122 made of a multilayer film is formed on a substrate 121, and a buffer layer 123a is formed on the reflective layer 122 as shown in FIG. As shown in (c), an absorber layer 124a is further formed on the buffer layer 123a.

Next, as shown in FIG. 13D, the absorber layer 124a is patterned by photolithography to form an absorber pattern 124. At this time, a two-step etching method is used. That is, first, dry etching is performed, and as shown in FIG.
Subsequent to 24a, the buffer layer 123a is etched, and the etching is stopped with a small amount of the buffer layer 123a left. Next, wet etching is performed, and FIG.
As shown in (2), the remaining buffer layer 123a is completely removed to expose the surface of the reflective layer 122. According to this method, overetching of the surface of the reflective layer can be minimized by employing wet etching having higher etching selectivity than dry etching.

The second method uses a photomask having the structure shown in FIG. 14 and is disclosed in PJSMangat et al., "EUV m
ask fabrication with Cr absorber ", Proceedings of S
PIEVol.3997, p.76,2000. In this photomask 140, a buffer layer 144 made of a silicon nitride oxide film (SiON) is formed below the absorber pattern 145, and a chromium (C
r) An etching stopper layer 143 made of a film is formed. When manufacturing the photomask 140, as shown in FIG. 15A, a reflective layer 142 composed of a multilayer film is formed on a substrate 141, and as shown in FIG.
An etching stopper layer 143a is formed on the reflective layer 142, and a buffer layer 144a is formed on the etching stopper layer 143a as shown in FIG.
As shown in (d), an absorber layer 145a is further formed on the buffer layer 144a.

Next, as shown in FIG. 15E, the absorber layer 145a is patterned by photolithography to form an absorber pattern 145, and thereafter, as shown in FIG.
As shown in FIG. 7, the buffer layer 144a is etched.
At this time, since the etching selectivity of SiON to Cr is high, the etching of the buffer layer 144a stops at the surface of the etching stopper layer 143a. Then, FIG.
(G), the etching stopper layer 14
3a is removed to expose the surface of the reflective layer 142. According to this method, the use of the etching stopper layer prevents the reflection layer surface from being over-etched when the buffer layer is etched.

[0010]

However, the above-mentioned 2)
Each method had its own problems. For example, the first method has a problem that an etching process is complicated because a two-stage etching method is used, and labor and time spent in the process are increased. Even though wet etching has a higher etching selectivity than dry etching, it is difficult to control the etching, and the surface of the reflective layer may be damaged depending on process conditions such as etching time.

On the other hand, in the second method, the process becomes complicated by forming an etching stopper layer,
Although the formation of the etching stopper layer can prevent overetching of the reflection layer surface when etching the buffer layer, there is a possibility that overetching of the reflection layer surface will occur when the etching stopper layer is removed in the next step. That is, if the etching stopper layer made of chromium is left on the reflection area, the chromium film has a strong light absorption property and the reflection on the surface of the reflection layer is hindered, so that the etching stopper layer itself is eventually removed. Must. At this time, if the etching selectivity between chromium and the film constituting the reflective layer surface is low, the reflective layer surface is over-etched.

The present invention has been made to solve the above-mentioned problems, and has been made without complicating the manufacturing process.
It is an object of the present invention to provide a reflective photomask that can prevent the surface of a reflective layer from being damaged in a manufacturing process.

[0013]

In order to achieve the above object, a reflection type photomask according to a first aspect of the present invention is formed on a substrate, and two different films are alternately laminated on the substrate. Layer formed of a multilayered film, a buffer layer formed of a metal film formed on the reflective layer, and an absorber pattern formed of a material capable of absorbing soft X-rays formed on the buffer layer with a predetermined pattern shape And characterized in that:

According to a second aspect of the present invention, there is provided a reflective photomask comprising a substrate, a reflective layer formed on the substrate, a multilayer film in which two different films are alternately laminated, and a reflective layer formed on the reflective layer. A buffer layer having a predetermined pattern shape, and an absorber pattern made of a material capable of absorbing soft X-rays formed on the buffer layer with the same pattern shape as the buffer layer. Features.

According to a third aspect of the present invention, there is provided a reflective photomask formed of a substrate, a reflective layer formed on the substrate, a multilayer film in which two kinds of different films are alternately laminated, and a reflective layer formed on the reflective layer. A first buffer layer made of a metal film formed on the first buffer layer and a second buffer layer formed on the first buffer layer and having a predetermined pattern shape.
And an absorber pattern made of a material capable of absorbing soft X-rays formed on the second buffer layer with the same pattern shape as the second buffer layer.

The present inventors have replaced a buffer layer made of a certain metal film with a buffer layer made of a semiconductor material such as a silicon oxide film (SiO _x ) or a silicon oxynitride film (SiON). When used, even if the buffer layer is left in the reflection region of the photomask, reflection on the surface of the reflection layer is not disturbed as much as the buffer layer made of a semiconductor material, and a high etching selectivity to the constituent material of the reflection layer is obtained. Was obtained.

According to this finding, since the buffer layer can be left in the reflection region of the photomask, the etching can be stopped before reaching the reflection layer surface when the absorber pattern is patterned. Therefore,
The surface of the reflective layer is not damaged, and the reflectance does not decrease. On the other hand, even when the buffer layer in the reflection region is removed, the etching selectivity to the constituent material of the reflection layer is high, so that the surface of the reflection layer is hardly damaged, and the reflectance does not decrease.

The present inventors have found that ruthenium is particularly suitable as the metal film constituting the buffer layer. The details will be described later in the section of [Embodiments of the Invention].
It was actually confirmed that when ruthenium was used, a high etching selectivity was obtained with respect to the constituent material of the reflective layer.
Further, it has been found that when the ruthenium buffer layer is left on the reflection region, if the thickness of ruthenium is set to 3 nm or less, the reflectance is improved rather than the case where the surface of the reflection layer is exposed.

In the structure in which the buffer layer is left in the reflection region, the etching of the absorber is stopped in the state of just etching, and the thickness of the buffer layer on the reflection region is the same as the thickness of the other region (absorption region). Even if the thickness of the buffer layer on the reflection region becomes smaller than that of the other region (absorption region) as a result of over-etching, there is no problem.

When a multilayer film constituting a reflection layer is formed on a substrate, an internal stress of either a compressive stress or a tensile stress is generated depending on the type of the multilayer film. Therefore, by providing a stress relaxation layer having an internal stress opposite to the internal stress of the reflective layer between the substrate and the reflective layer, the internal stress of the reflective layer is offset and reduced, and the warpage of the photomask is prevented. Can be.

As the two kinds of films constituting the reflection layer, the combination of a molybdenum film and a silicon film is the most suitable because the difference in refractive index is the largest and the reflectance is the highest.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a cross-sectional view showing a reflective photomask of the present embodiment, and FIG. 2 is a process cross-sectional view for explaining a method of manufacturing the reflective photomask. In the following cross-sectional views including FIGS. 1 and 2, the thickness ratio of each layer constituting the photomask is different from the actual one for convenience of illustration. In this embodiment, an example of a mode in which a buffer layer made of a metal film is left over a reflective region will be described.

The reflection type photomask 10 of the present embodiment
As shown in FIG. 1, a reflective layer 12 composed of a multilayer film in which a molybdenum (Mo) film and a silicon (Si) film are alternately laminated on a substrate 11 made of silicon, glass, or the like. The uppermost layer of the reflective layer 12 may be either a molybdenum film or a silicon film, but it is preferable to use a silicon film as the uppermost layer because a natural oxide film formed on the silicon surface has high stability. The thickness of the single layer of molybdenum and silicon can be arbitrarily set to about several nm, and the number of laminations can be set to about several tens layers.

Incidentally, the film constituting the reflection layer 12 includes:
Instead of molybdenum, scandium (Sc), titanium (Ti), vanadium (V), iron (Fe), nickel (Ni), cobalt (Co), zirconium (Zr),
Niobium (Nb), Technetium (Tc), Ruthenium (Ru) Rhodium (Rh), Hafnium (Hf), Tantalum (Ta), Tungsten (W), Rhenium (R
e), osmium (Os), iridium (Ir), platinum (Pt), copper (Cu), palladium (Pd), silver (A
g), gold (Au) or the like, and silicon carbide, silicon nitride, silicon oxide, boron nitride, beryllium nitride, beryllium oxide, aluminum nitride, aluminum oxide, or the like is used instead of silicon.

Ruthenium (Ru) is formed on the entire surface of the reflective layer 12.
Is formed, and the Ru buffer layer 1 is formed.
Absorber pattern 14 having a predetermined pattern is formed on 3. In the reflective photomask 10, a region where the absorber pattern 14 is formed is an absorption region A that absorbs EUV light, and a region where there is no absorber pattern 14 and the surface of the Ru buffer layer 13 is exposed is a reflection region R. . Ru
The thickness of the buffer layer 13 can be arbitrarily set in a range from several nm to several tens of nm.
In addition to Ru, materials such as Pt, Ir, and Pd can be used.

As the absorber pattern 14, tantalum nitride (TaN), tantalum (Ta), chromium (Cr), titanium nitride (TiN), titanium (Ti), aluminum
Copper alloy (Al-Cu), NiSi, TaSiN, TiS
iN, aluminum (Al), or the like can be used.
The thickness of the absorber pattern 14 is desirably 200 nm or less.

Hereinafter, the reflection type photomask 10 having the above configuration will be described.
A method of manufacturing the device will be described. First, as shown in FIG. 2A, a reflection layer 12 made of a Mo / Si multilayer film is formed on the entire surface of a substrate 11. In this case, for example, an RF magnetron sputtering method or an ion beam sputtering method is used as a film formation method. The sputtering conditions vary depending on the equipment used. A film is formed by switching between Mo and Si at a cycle of 7 nm so as to have the highest reflectance in a wavelength region of 13.4 nm. The ratio of Mo in one cycle is about 40%, the thickness of Mo is about 2.8 nm, and the thickness of Si is about 4.2 nm. As for the number of layers, first, 40 layers of Mo / Si are formed, and then Si is finally formed, so that the total number of layers is 81.

Next, as shown in FIG.
A buffer layer 13 made of Ru is formed on the entire surface of the substrate 2.
In this case, a DC sputtering method was used, and the sputtering conditions were, for example, DC power: 1 kW and pressure: 0.3.
The atmosphere is a Pa, Ar gas atmosphere.

Next, as shown in FIG.
An absorber layer 14a of TaN or the like is formed on the entire surface of the u buffer layer 13.
Is formed. At this time, when the material of the absorber layer 14a is a nitride, a reactive sputtering method is used, and in other cases, a DC sputtering method is used.

Next, as shown in FIG. 2D, the absorber layer 14a is patterned by photolithography to form an absorber pattern 14. At this time, after a resist pattern (not shown) having a desired pattern shape is formed on the absorber layer 14a, using this resist pattern as a mask, an ECR reactive etching method is used.
When the material of the absorber layer 14a is TaN, for example, an ECR method is used, and the used gas is Cl ₂ / Ar = 80/40 ml / mi.
n, ECR power: 600 W, RF bias power: 3
The absorber layer 14a is etched under the conditions of 0 W, pressure: 5 Pa, and substrate temperature: 50 ° C. In the etching process of the absorber layer 14a, if the etching is stopped in a state of just etching, the Ru buffer layer 13
Becomes the same as the film thickness of the other region (absorption region). On the other hand, if slight over-etching is performed, FIG.
As a result, as shown in FIG.
Although the film thickness of No. 3 is smaller than that of the other region (absorption region), there is no problem even if such a film is formed. Thereafter, mask repair using FIB is performed as needed. For mask repair, FIB and GAE (gas-assisted etching)
Can also be used. In that case, Br ₂ is mainly used as an etching gas, but can be appropriately changed depending on the material of the absorber and the buffer layer. Through the above steps, the reflective photomask 10 of the present embodiment is completed.

According to the present embodiment, the Ru buffer layer 13 on the reflection region is left without complicating the manufacturing process unlike the conventional example using the two-step etching. 12 can reliably prevent damage to the surface and does not cause a decrease in reflectance.

However, in the case of the present embodiment, since the Ru buffer layer 13 exists on the reflection region, there is a concern that the reflectance may be reduced. FIG. 10 is a simulation result showing the dependency of the reflectance on the film thickness when SiO ₂ and Ru are used as the buffer layer left on the reflection layer.
m), the vertical axis is the reflectance. The simulation conditions are
From the top, the laminated structure of the reflective layer is SiO ₂ (assuming a natural oxide film on Si, film thickness 2 nm), Si (film thickness 4.14 nm) /
It is assumed that buffer layers of SiO ₂ and Ru are respectively laminated on a multilayer film in which 40 layers of Mo (film thickness 2.76 nm) are laminated, the EUV light wavelength is 13.5 nm, and the light incident angle is 0 °. did.

In the case of the SiO ₂ buffer layer (shown by a broken line in the figure), the reflectance tends to gradually decrease from about 0.75 as the film thickness increases, although the curve is slightly wavy.
On the other hand, in the case of the Ru buffer layer (shown by a solid line in the figure), the wave of the curve becomes larger than in the case of SiO ₂ ,
It was found that when the thickness t was in the range of 0 <t ≦ 3 nm, the reflectance was improved more than when no buffer layer was provided. Therefore, in the case where the Ru buffer layer is left, for example, the film thickness is about 6 nm if the point where the reflectance is reduced by 10% as compared with the case where there is no buffer layer is set to the desired reflectance in the photomask to be manufactured. The film thickness can be appropriately set according to the conditions. As described above, the thickness of the Ru buffer layer is desirably 3 nm or less from the viewpoint that the reflectance can be increased as compared with the case where the buffer layer is not provided.

[Second Embodiment] Hereinafter, a second embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. FIG. 4 is a sectional view showing a reflection type photomask of the present embodiment, and FIG.
FIG. 4 is a process cross-sectional view for describing the method for manufacturing the reflection type photomask. In the present embodiment, an example will be described in which the buffer layer made of a metal film is not left on the reflection region, contrary to the first embodiment.

The reflection type photomask 20 of the present embodiment
As shown in FIG. 4, a reflective layer 22 made of a Mo / Si multilayer film is formed on a substrate 21 made of silicon, glass or the like. As the material of the reflection layer 22, other than Mo / Si, the same material as exemplified in the first embodiment can be used. The thickness and the number of layers of the single layer of molybdenum and silicon are the same as in the first embodiment.

A buffer layer 23 made of ruthenium (Ru) having a predetermined pattern shape is formed on the reflective layer 22, and an absorber pattern 24 having the same pattern shape as the Ru buffer layer 23 is formed on the Ru buffer layer 23. Is formed. In the reflection type photomask 20, the area covered with the absorber pattern 24 is the absorption area A, and the area where the absorber pattern 24 and the Ru buffer layer 23 are not present and the surface of the reflection layer 22 is exposed is the reflection area R. The material and thickness of the buffer layer 23 other than Ru may be the same as in the first embodiment. The material and thickness of the absorber pattern 24 may be the same as in the first embodiment.

Hereinafter, the reflection type photomask 20 having the above configuration will be described.
A method of manufacturing the device will be described. First, as shown in FIG. 5A, a reflective layer 22 made of a Mo / Si multilayer film is formed on the entire surface of a substrate 21. In this case, for example, an RF magnetron sputtering method or an ion beam sputtering method is used as a film formation method. The sputtering conditions vary depending on the equipment used. A film is formed by switching between Mo and Si at a cycle of 7 nm so as to have the highest reflectance in a wavelength region of 13.4 nm. The ratio of Mo in one cycle is about 40%, the thickness of Mo is about 2.8 nm, and the thickness of Si is about 4.2 nm. As for the number of layers, first, 40 layers of Mo / Si are formed, and then Si is finally formed, so that the total number of layers is 81.

Next, as shown in FIG.
A buffer layer 23a made of Ru is formed on the entire surface of the substrate 2. In this case, a DC sputtering method is used, and the sputtering conditions are, for example, DC power: 1 kW, pressure:
0.3 Pa in an Ar gas atmosphere.

Next, as shown in FIG.
An absorber layer 24 of TaN or the like is formed on the entire surface of the u buffer layer 23a.
a is formed. At this time, when the material of the absorber layer 14a is a nitride, a reactive sputtering method is used, and in other cases, a DC sputtering method is used.

Next, as shown in FIG. 5D, the absorber layer 24a is patterned by photolithography to form an absorber pattern 24. At this time, after a resist pattern (not shown) having a desired pattern shape is formed on the absorber layer 24a, using this resist pattern as a mask, an ECR reactive etching method is used.
When the material of the absorber layer 14a is TaN, for example, an ECR method is used, and the used gas is Cl ₂ / Ar = 80/40 ml / mi.
n, ECR power: 600 W, RF bias power: 3
The absorber layer 24a is etched under the conditions of 0 W, pressure: 5 Pa, and substrate temperature: 50 ° C. until at least the surface of the Ru buffer layer 23a is exposed. In the case of the present embodiment, the Ru buffer layer 23a is also etched after this, so that either just etching or over etching may be used. Thereafter, mask repair using FIB is performed as needed.

Next, as shown in FIG. 5E, the Ru buffer layer 23a is etched using the absorber pattern 24 as a mask. In the case of the present embodiment, a problem here is that the reflective layer 22 is etched when the Ru buffer layer 23a is etched.
Is that there is no damage to the surface. The present inventors used an ECR (Electron Cycrotron Resonance) type dry etching apparatus and used gas: Cl ₂ / O ₂ (C
l ₂ content: 30%), ECR power: 300 W, RF
When the Ru buffer layer was actually etched under the conditions of a bias power of 30 W and a substrate temperature of 50 ° C., it was as high as 19.3: 1 with respect to amorphous Si (the uppermost layer of the reflective layer) formed by the sputtering method. An etching selectivity was obtained.

Further, the conventional buffer layer material of SiO
₂ and Ru used in the present embodiment were compared in terms of etching selectivity in etching TaN as a material of the absorber layer. Working gas: Cl ₂ / Ar = 80/40 ml / min, E
CR power: 600 W, RF bias power: 30 W,
When etching was actually performed under the conditions of a pressure: 5 Pa and a substrate temperature: 50 ° C., the etching selectivity was 8: 1 with respect to SiO ₂ , but 30: with respect to Ru.
A high etching selectivity of 1 was obtained.

As described above, according to the present embodiment, the first
Different from the embodiment, the Ru buffer layer 23 on the reflection region
Even if a is etched or removed, over-etching of the surface of the reflective layer 22 can be sufficiently suppressed by controlling the etching conditions, and a decrease in reflectance can be prevented.

[Third Embodiment] Hereinafter, a third embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. FIG. 6 is a sectional view showing a reflection type photomask of the present embodiment, and FIG.
FIG. 4 is a process cross-sectional view for describing the method for manufacturing the reflection type photomask. In this embodiment, an example in which a second buffer layer made of a semiconductor material is formed over a first buffer layer made of a metal film will be described.

The reflection type photomask 30 of the present embodiment
As shown in FIG. 6, a reflective layer 32 made of a Mo / Si multilayer film is formed on a substrate 31 made of silicon, glass, or the like. As the material of the reflection layer 32, other than Mo / Si, the same material as exemplified in the first embodiment can be used. The thickness and the number of layers of the single layer of molybdenum and silicon are the same as in the first embodiment.

Ruthenium (Ru) is formed on the entire surface of the reflective layer 32.
Is formed, a second buffer layer having a predetermined pattern is formed on the first buffer layer 33, and an absorber pattern 35 is formed on the second buffer layer. Is formed. In the entire surface of the reflective photomask 30, the area covered with the absorber pattern 35 is the area where the absorber area A, the absorber pattern 35 and the second buffer layer 34 are not present, and the surface of the first buffer layer 33 is exposed. Becomes the reflection region R. The material and thickness of the first buffer layer 33 other than Ru may be the same as in the first embodiment. As the material of the second buffer layer 34, any of a silicon oxide film, a silicon nitride film, and a silicon oxynitride film can be used. The thickness of the second buffer layer 34 may be about several tens to 100 nm. Absorber pattern 35
The material and the film thickness may be the same as in the first embodiment.

Hereinafter, the reflection type photomask 30 having the above configuration will be described.
A method of manufacturing the device will be described. First, as shown in FIG. 7A, a reflective layer 32 made of a Mo / Si multilayer film is formed on the entire surface of a substrate 31. In this case, for example, an RF magnetron sputtering method or an ion beam sputtering method is used as a film formation method. The sputtering conditions vary depending on the equipment used. A film is formed by switching between Mo and Si at a cycle of 7 nm so as to have the highest reflectance in a wavelength region of 13.4 nm. The ratio of Mo in one cycle is about 40%, the thickness of Mo is about 2.8 nm, and the thickness of Si is about 4.2 nm. As for the number of layers, first, 40 layers of Mo / Si are formed, and then Si is finally formed, so that the total number of layers is 81.

Next, as shown in FIG.
A first buffer layer 33 made of Ru is formed on the entire surface of the substrate 2. In this case, a DC sputtering method is used, and the sputtering conditions are, for example, DC power: 1 kW, pressure:
0.3 Pa in an Ar gas atmosphere.

Next, as shown in FIG. 7 (c), forming a second buffer layer 34a made of SiO _x or the like on the entire surface of the first buffer layer 33. In this case, low-temperature deposition is advantageous in order to minimize the change in the reflectance of the reflective layer. Therefore, a sputtering method or a plasma CVD method is used. For low-temperature deposition, RF sputtering is mainly used for SiO _x , and plasma CVD is mainly used for SiON.

Next, as shown in FIG. 7D, an absorber layer 35a made of TaN or the like is further formed on the entire surface of the second buffer layer 34a. At this time, when the material of the absorber layer 14a is a nitride, a reactive sputtering method is used, and in other cases, a DC sputtering method is used.

Next, as shown in FIG. 7E, the absorber layer 35a is patterned by photolithography to form an absorber pattern 35. In this case, after a resist pattern (not shown) having a desired pattern shape is formed on the absorber layer 35a, the resist pattern is used as a mask by an ECR reactive etching method.
When the material of the absorber layer 14a is TaN, for example, an ECR method is used, and the used gas is Cl ₂ / Ar = 80/40 ml / mi.
n, ECR power: 600 W, RF bias power: 3
The absorber layer 35a is etched under the conditions of 0 W, pressure: 5 Pa, and substrate temperature: 50 ° C. until at least the surface of the second buffer layer 34a is exposed. Thereafter, mask repair using FIB is performed as needed.

Next, as shown in FIG. 7F, the second buffer layer 34a is etched using the absorber pattern 35 as a mask. In this case, the second buffer layer 34a
When the material is SiO _x, the gas used is, for example, ECR method: Ar / C ₄ F ₈ / O ₂ = 200/10 / 20m
1 / min, ECR power: 600 W, RF bias power: 15 W, pressure: 1 Pa, substrate temperature: 50 ° C. The etching of the second buffer layer 34 a is performed until at least the surface of the first buffer layer 33 is exposed. Do. Also,
When the material of the second buffer layer 34a is SiON,
Etching can be performed using a fluorine-based etching gas. In this etching step, the first buffer layer 33 functions as an etching stopper. When the present inventor actually performed etching, the etching rate of the SiO _x film was 70 nm / min or more when Ar / C ₄ F ₈ / O ₂ gas was used as the etching gas. On the other hand, in the case of the Ru film, it was confirmed that even the same etching gas was used, only a very small amount that could not be measured was etched, and that the Ru film sufficiently functioned as an etching stopper. Depending on the etching conditions, as shown in FIG. 8, the surface of the first buffer layer 33 is slightly etched, and the thickness of the first buffer layer 33 on the reflection region is smaller than that of the other region (absorption region). It can be, but is not a problem. Through the above steps, the reflective photomask 30 of the present embodiment is completed.

According to the present embodiment, the first buffer layer 33 of Ru on the reflection region is left without complicating the manufacturing process unlike the conventional example using two-step etching. An effect similar to that of the first embodiment is obtained, in which damage to the surface of the reflective layer 32 in the process can be reliably prevented, and the reflectance does not decrease.
Further, as in the first embodiment, even if there is a concern that the reflectance may decrease due to the existence of the first buffer layer 33 of Ru on the reflection region, the problem can be sufficiently solved by controlling the film thickness. Can be avoided. From the viewpoint that the reflectance can be increased as compared with the case where there is no buffer layer, the film thickness is desirably 3 nm or less.

[Fourth Embodiment] Hereinafter, a fourth embodiment of the present invention will be described.
The embodiment will be described with reference to FIG. FIG. 9 is a cross-sectional view showing the reflective photomask of the present embodiment. The configuration of the reflection type photomask of this embodiment is almost the same as that of the first embodiment, and the only difference is that a stress relaxation layer is added between the substrate and the reflection layer. Therefore, in FIG. 9, the same reference numerals are given to the same components as those in FIG.

The reflection type photomask 40 of the present embodiment.
Is a substrate 1 made of Si, glass or the like as shown in FIG.
1, a stress relaxation layer 41 is formed, and on the stress relaxation layer 41, a reflection layer 12 made of a Mo / Si multilayer film is formed. Then, the Ru buffer layer 13 is formed on the reflective layer 12, and the absorber pattern 14 is formed thereon, as in the first embodiment. Examples of the material used for the stress relaxation layer 41 include Ru, Mo, and the like.

Also in the present embodiment, the first embodiment, in which the reflection of the surface of the reflective layer in the production process can be reliably prevented without complicating the production process, and the reflectance does not decrease. The same effect can be obtained. In addition, in the case of the present embodiment, the direction of the internal stress of the reflection layer 12 made of the Mo / Si multilayer film and the direction of the internal stress of the stress relaxation layer 41 made of the single layer film of Ru, Mo, etc. are opposite. In addition, the internal stress of the reflection layer 12 is offset and alleviated, and the warpage of the photomask can be prevented.

The technical scope of the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention. For example, the specific descriptions of the materials and film thicknesses of the respective layers, the various process conditions in the manufacturing process, and the like illustrated in the above-described embodiment are merely examples, and can be appropriately changed.

[0058]

As described above in detail, according to the reflection type photomask of the present invention, it is possible to prevent the reflection layer surface from being damaged in the production process without complicating the production process, and to reduce the reflectance. Can be prevented. As a result, it becomes suitable for fine processing using the exposure wavelength in the EUV region.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a reflective photomask according to a first embodiment of the present invention.

FIG. 2 is a process cross-sectional view showing a manufacturing process of the reflective photomask in order.

FIG. 3 is a sectional view showing another example of the reflection type photomask.

FIG. 4 is a cross-sectional view illustrating a reflective photomask according to a second embodiment of the present invention.

FIG. 5 is a process sectional view showing the manufacturing process of the reflection type photomask in order.

FIG. 6 is a cross-sectional view illustrating a reflection type photomask according to the first embodiment of the present invention.

FIG. 7 is a process sectional view sequentially showing a manufacturing process of the reflection type photomask.

FIG. 8 is a sectional view showing another example of the reflection type photomask.

FIG. 9 is a cross-sectional view illustrating a reflective photomask according to the first embodiment of the present invention.

FIG. 10 is a simulation result showing the dependency of the reflectance on the film thickness when SiO ₂ and Ru are used as the buffer layer.

FIG. 11 is a cross-sectional view illustrating an example of a conventional reflective photomask.

FIG. 12 is a cross-sectional view illustrating another example of a conventional reflective photomask.

FIG. 13 is a process sectional view showing the manufacturing process of the reflection type photomask in order.

FIG. 14 is a cross-sectional view showing still another example of a conventional reflective photomask.

FIG. 15 is a process sectional view showing the manufacturing process of the reflection type photomask in order.

FIG. 16 is a view for explaining a state of a mask repair step.

[Explanation of symbols]

 10, 20, 30, 40 Reflective photomask 11, 21, 31 Substrate 12, 22, 32 Reflective layer 13, 23, 23a Buffer layer 14, 24, 35, 35a Absorber pattern 14a, 24a Absorber layer 33 First Buffer layer 34, 34a second buffer layer 41 stress relaxation layer A absorption region R reflection region

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Lee Byungsawa 3-1 Morinosato Wakamiya, Atsugi City, Kanagawa Prefecture NTT Atsugi R & D Center Technology Research Association Super-advanced Electronics Technology Development Organization (72) Inventor Taro Ogawa Kokubunji, Tokyo 1-280 Higashi-Koigakubo, Hitachi, Ltd. Central Research Laboratory, Hitachi, Ltd. (72) Eiichi Hoshino 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa F-term in Fujitsu Limited (Reference) 2H095 BA01 BA07 BA10 BB01 BB35 BC05 BC11 BC24 5F046 GD05 GD10 GD15 GD16

Claims (12)

[Claims] 1. A substrate, and a reflective layer formed on the substrate and comprising a multilayer film in which two different films are alternately stacked,
A buffer layer made of a metal film formed on the reflective layer; and an absorber pattern made of a material capable of absorbing soft X-rays formed on the buffer layer with a predetermined pattern shape. Reflective photomask. 2. The reflective photomask according to claim 1, wherein the metal film forming the buffer layer is ruthenium. 3. The reflective photomask according to claim 2, wherein said ruthenium metal film has a thickness of 3 nm or less. 4. The buffer layer according to claim 1, wherein a thickness of the buffer layer in a region where the absorber pattern is not formed is smaller than a thickness of the buffer layer in another portion. The reflective photomask according to claim 1. 5. A substrate, and a reflective layer formed on the substrate and comprising a multilayer film in which two different films are alternately stacked,
A buffer layer formed of a metal film formed on the reflective layer and having a predetermined pattern shape; and a material capable of absorbing soft X-rays formed on the buffer layer with the same pattern shape as the buffer layer. A reflective photomask comprising an absorber pattern. 6. The reflective photomask according to claim 5, wherein the metal film forming the buffer layer is ruthenium. 7. A substrate, and a reflective layer formed on the substrate and formed of a multilayer film in which two different films are alternately stacked,
A first buffer layer made of a metal film formed on the reflective layer, a second buffer layer formed on the first buffer layer and having a predetermined pattern, and a second buffer layer. A reflector pattern formed of a material capable of absorbing soft X-rays formed on the second buffer layer with the same pattern shape. 8. The reflection type photomask according to claim 7, wherein the metal film forming the first buffer layer is ruthenium. 9. The reflection type photomask according to claim 8, wherein the thickness of the ruthenium metal film is 3 nm or less. 10. The film thickness of the first buffer layer in a region where the absorber pattern is not formed is smaller than the film thickness of the first buffer layer in another portion. Item 10. The reflective photomask according to any one of Items 7 to 9. 11. The reflection type photomask according to claim 1, wherein the two different films forming the reflection layer are a molybdenum film and a silicon film. 12. A stress relief layer provided between the substrate and the reflection layer to offset and relieve internal stress of the reflection layer. The reflective photomask according to claim 1.